Generally, support devices for a portion of the anatomy of a patient that have been employed in medical procedures have emphasized stability and rigidity in their structures at the expense of ease of adjustment in view of the recognized importance in guarding against undesired movement of the patient during the medical procedure being carried out. For example, in U.S. Pat. No. 4,157,876, a lockable, universally articulated joint in an orthopaedic appliance is disclosed. A locking member is also provided which includes a locking screw which extends through a socket and is threaded into a locking device. When the locking screw is loosened, the locking member allows universal articulation between the movable elements while preventing separation of these elements. Tightening of the screw effects clamping of the movable elements. Such a device as well as others of a similar nature do not provide the precise positioning and any facility in repositioning of the surgical site such as the head of a patient when used in conjunction with a headrest required in neurological surgery. See in this regard, U.S. Pat. No. 4,585,195 and Canadian Patent No. 823556. While these and similar devices have enabled the user to securely lock in a desired position the object upon which a procedure is to be carried out, they also generally suffer from the disadvantage of consuming a considerable amount of time to effect the original positioning and render impractical repositioning of the object during the operating procedure. This is a particularly serious disadvantage in neurological surgery, as such procedures generally consume a lengthy amount of time, so that where repositioning cannot be readily accomplished, the surgeon is required to operate in awkward positions which can greatly contribute to fatigue and result in lengthening of the time required to carry out the procedure. Where a device incorporates a plurality of universal joints, each of which must be separately and manually locked and unlocked to effect repositioning, there is always the possibility of overlooking one of the locking devices in carrying out any repositioning that is effected thus increasing the potential for injury to the patient.